/**
 *    Copyright (C) 2025-present MongoDB, Inc.
 *
 *    This program is free software: you can redistribute it and/or modify
 *    it under the terms of the Server Side Public License, version 1,
 *    as published by MongoDB, Inc.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    Server Side Public License for more details.
 *
 *    You should have received a copy of the Server Side Public License
 *    along with this program. If not, see
 *    <http://www.mongodb.com/licensing/server-side-public-license>.
 *
 *    As a special exception, the copyright holders give permission to link the
 *    code of portions of this program with the OpenSSL library under certain
 *    conditions as described in each individual source file and distribute
 *    linked combinations including the program with the OpenSSL library. You
 *    must comply with the Server Side Public License in all respects for
 *    all of the code used other than as permitted herein. If you modify file(s)
 *    with this exception, you may extend this exception to your version of the
 *    file(s), but you are not obligated to do so. If you do not wish to do so,
 *    delete this exception statement from your version. If you delete this
 *    exception statement from all source files in the program, then also delete
 *    it in the license file.
 */

#pragma once

#include "mongo/base/string_data.h"
#include "mongo/db/exec/agg/stage.h"
#include "mongo/db/operation_context.h"
#include "mongo/db/pipeline/document_source.h"
#include "mongo/db/pipeline/expression_context.h"
#include "mongo/db/query/query_settings/query_settings_gen.h"
#include "mongo/db/query/query_settings/query_settings_service.h"
#include "mongo/db/query/query_shape/query_shape.h"
#include "mongo/stdx/unordered_map.h"
#include "mongo/util/modules.h"

#include <boost/smart_ptr/intrusive_ptr.hpp>

namespace mongo::exec::agg {
using QueryShapeConfigurationMap = stdx::unordered_map<query_shape::QueryShapeHash,
                                                       query_settings::QueryShapeConfiguration,
                                                       QueryShapeHashHasher>;

class QuerySettingsStage final : public Stage {
public:
    static constexpr StringData kDebugQueryShapeFieldName = "debugQueryShape"_sd;

    /**
     * The possible states of the stage. First we are reading all the 'config.representativeQueries'
     * collection and return all QueryShapeConfigurations that have representative queries. Once the
     * cursor is exhausted, we iterate over the remaining configurations in the
     * '_queryShapeConfigsMap'.
     */
    enum class State {
        kReadingFromQueryShapeRepresentativeQueriesColl,
        kReadingFromQueryShapeConfigsMap
    };

    QuerySettingsStage(StringData stageName,
                       const boost::intrusive_ptr<ExpressionContext>& pExtCtx,
                       bool showDebugQueryShape);

    void detachFromOperationContext() final;
    void reattachToOperationContext(OperationContext* opCtx) final;

private:
    GetNextResult doGetNext() final;
    void doDispose() final;

    /**
     * DocumentSource that holds a cursor over the 'queryShapeRepresentativeQueries' collection:
     * - either on local node if we are in the replica set
     * - or on the configsvr if we are in the sharded cluster deployment.
     *
     * If gFeatureFlagPQSBackfill is disabled, returns empty DocumentSourceQueue.
     */
    boost::intrusive_ptr<DocumentSource> createQueryShapeRepresentativeQueriesCursor(
        OperationContext* opCtx);

    boost::intrusive_ptr<exec::agg::Stage> _queryShapeRepresentativeQueriesCursor;
    QueryShapeConfigurationMap _queryShapeConfigsMap;
    QueryShapeConfigurationMap::const_iterator _iterator;
    bool _showDebugQueryShape;
    State _state = State::kReadingFromQueryShapeRepresentativeQueriesColl;
};

}  // namespace mongo::exec::agg
